Trudel, David

Wormuth, Mattias

Scheringer, Martin

Abstract [en]

The exposure of humans to perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) was quantified with emphasis on assessing the relative importance of metabolic transformation of precursor compounds. A Scenario-Based Risk Assessment (SceBRA) approach was used to model the exposure to these compounds from a variety of different pathways, the uptake into the human body and resulting daily doses. To capture the physiological and behavioral differences of age and gender, the exposure and resulting doses for seven consumer groups were calculated. The estimated chronic doses of a general population of an industrialized country range from 3.9 to 520 ng/(kg day) and 0.3 to 140 ng/(kg day) for PFOS and PFOA, respectively. The relative importance of precursor-based doses of PFOS and PFOA was estimated to be 2–5% and 2–8% in an intermediate scenario and 60–80% and 28–55% in a high-exposure scenario. This indicates that sub groups of the population may receive a substantial part of the PFOS and PFOA doses from precursor compounds, even though they are of low importance for the general population. Similar to a preceding study, uptake of perfluorinated acids from contaminated food and drinking water was identified as the most important pathway of exposure for the general population. The biotransformation yields of telomer-based precursors and to a lesser extent perfluorooctanesulfonylfluoride-based precursors were identified as influential parameters in the uncertainty analysis. Fast food consumption and fraction of food packaging paper treated with PFCs were influential parameters for determining the doses of PFOA.

Vestergren, Robin

Abstract [en]

Perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkane sulfonic acids (PFSAs) are persistent organic contaminants which have been globally measured in human serum samples at low μg L-1 concentrations. One hypothesis, the so-called "indirect hypothesis", postulates that exposure to precursor compounds is responsible for the presence of PFCAs and PFSAs in human serum. The main purpose of this thesis was to test an alternative hypothesis that direct intake of PFCAs and PFSAs via the diet is the dominant ongoing pathway of exposure. Exposure modeling results in paper I and II demonstrate that dietary intake is the major exposure pathway of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), while known precursors account for only a few percent of the total exposure. To address the uncertainties related to dietary intake pathways, highly sensitive analytical methods for a range of PFCAs and PFSAs are developed, validated and applied in paper III and IV. By the development of a novel analytical technique in paper III, detection limits in the pg g-1 range are achieved for a wide range of analytes in different food categories. Analysis of a large set of food basket samples from the Swedish market in paper IV shows that the concentrations in many dietary samples are lower than those used to estimate exposure to PFOA and PFOS in paper I and II. However, an updated dietary intake estimate in paper IV supports the conclusion of paper I and II that dietary intake is the major ongoing human exposure pathway for the general population. Pharmacokinetic modeling undertaken in paper II was reevaluated in this thesis and back-calculated daily intakes from serum concentrations of PFOA and PFOS are shown to be in agreement with the estimated dietary intakes from paper IV. However, due to uncertainties and simplifying assumptions in the pharmacokinetic model, it is possible that there are additional pathways of human exposure contributing to human serum levels.

Harrad, Stuart

Supervisors

Cousins, Ian T.

Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.Available from: 2011-11-10 Created: 2011-10-26 Last updated: 2011-10-31Bibliographically approved